AbstractBackground:Several factors may contribute to poorer prognosis for obese breast cancer patients, including unfavorable disease features, the influence of fat on estrogen availability, co-morbidity, and socio-demographic factors. Both obesity and estrogen receptor negative (ER-) tumors are more prevalent in black women than in whites in North America. We evaluated obesity and race in relation to outcomes in women with ER-breast cancer.

Methods:Among 4077 women from National Surgical Adjuvant Breast and Bowel Project clinical trials for node-negative, ER-breast cancer, we evaluated disease-free survival (DFS) and its constituents (tumor recurrence, contralateral breast cancer (CBC), second primary cancers, deaths prior to these events) and mortality in relation to body mass index (BMI) and race, using statistical modeling to account for other prognostic factors.

Conclusions:For women with node-negative, ER-breast cancer from clinical trials, obesity did not increase recurrence risk, but was associated with greater risk for second cancers, CBC, and mortality, particularly non-breast cancer deaths. Less favorable prognosis for black women persists in clinical trials, and is in part attributable to non-breast cancer outcomes.